If you want another idea for stabilizing your camera that is ultra portable, as in it will fit in any small bag or maybe even your pocket, look no further than the Platypod Max Camera Support. (There are smaller, cheaper versions available too.)
The Platypod Pro Max Camera Support is a wide, stable, and ultra low-profile platform that allows you to set up a large tripod head, camera, and lens on both horizontal and vertical surfaces.
Measuring 5.3 x 7.8" and only 0.2" thick, the Pro Max Camera Support allows you to photograph or record with a camera that is elevated only slightly higher than the tripod head it is used with. Four reversible, spiked feet that each feature rubber tips on one end can be distributed among five strategically placed, 1/4"-20 threaded holes. Once installed, they can be adjusted to level the platform on uneven surfaces, both indoors and out. For placement on unconventional surfaces and angles, two 2-inch belt shots allow the Pro Max Camera Support to be secured to a cylindrical object or to be taped onto angled floors. Two nail holes are included for permanent or semi-permanent mounting to walls, boards or ceilings; and for quick placement and removal from conventional tripods or quick release devices, 1/4"-20 and 3/8"-16 threaded holes are on the underside of the platform. You will need a bullhead for this unit, but when you want a stable camera and can't bring a tripod, this is often a great substitute.
I also like to shoot from my car, using it as a blind. For this the Kirk WM-2 Multi-Purpose Window Mount for Tripod Head (you have to supply your own head) is the best unit I've ever tested. It gives you a super stable shooting platform. If you prefer, the Apex Mini Bean Bag functions almost as well, but does take practice to get used to.
As for camera straps - I like the Peak Design Slide Camera Strap SL-T-2 because it can quickly clip on or off and will hold the Olympus camera body with the 300mm f/4 Pro Lens.
I don't use many actual filters on my lenses, but there are times I want a polarizer. My favorite is the Singh-Ray 77mm LB Warming Circular Polarizer Thin Mount Filter. It's great for cutting reflections and warming a scene. 77mm with step down rings can be used on most lenses.
The ThinkTank Airport Security V 2.0 Rolling Camera Bag is far and away my favorite travel bag. It holds all my bird photography gear and can be either rolled through an airport or carried on my back. It's very versatile, strong, and flexible.
When I am traveling light, or need to have a smaller carry-on (as required in international travel or for flights on regional jets) I use the ThinkTank Airport Advantage. It's smaller than the Security model and will fit under the seat of any regional jet I've ever flown on.
When I have to ship my gear, I rely exclusively on the Pelican 1614 Waterproof 1610 Case with Dividers or the Pelican 1510 Carry-On Case with Foam Set. I have never had a single piece of gear damaged when using Pelican cases.
Digital Darkroom Hardware
While it may only be temporary, I still use Apple computers for all my editing. Changes in Apple's approach has me considering going to Windows 10 full time (I currently use it part time), but for now I use the MacBookPro as my laptop of choice and the Microsoft Surface Studio - which has a bigger screen to work on at home or office. If you want something smaller, the Microsoft Surface Laptop is better than you think it is and it's superior to the outdated, MacBook Air.
One place where I generally prefer Windows is my tablet. I use the well-reviewed Microsoft Surface Pro 4 - I prefer this to Apple’s iPad mostly because it has a USB port. I still use an iPad 10.5 Pro for some applications. I do still prefer the Apple OS.
When it comes to storage, redundancy and backup, I currently recently switched to LaCie 4TB Rugged Thunderbolt / USB-C Mobile HDD. These are cheap and very portable. I have a dozen of them and use them now with confidence, since I've been traveling with them and they are very sturdy.
Digital Darkroom Software
I use a variety of software to edit my images. I used to use Aperture from Apple but when they abandoned it, I switched to Adobe Photoshop/Lightroom CC. I will use LR until Skylum issues their update to Luminar with a self-contained Digital Asset Manager (DAM.)
For most photo editing, I use Macphun Luminar.
While not absolutely necessary, the Olympus HLD-9 Power Battery Grip certainly is helpful in several ways. It makes shooting verticals (handheld) mach more comfortable. It adds bulk to the camera which is a good thing for some of us who have bigger hands. And it stores a second battery. I keep one body with the battery grip in my bag and one without.