I learned a long time ago that engineering minds think alike. And I am reminded of it every time I see one of my ideas independently thought of by someone else. It's happened so many times I've often joked that I should wear a tin foil hat to keep people from stealing my ideas right out of my head. But the reality is that us engineers all have a similar education and skills, and a similar toolbox of ideas and technologies to pull from when we see a problem that needs solving, and we come up with similar solutions when we see an opportunity.
I have a folder in my web browser with links to all the things I thought of first but never acted on and eventually someone else did. There's probably like 50 things in that folder now. Some are just project ideas like Dave's logic analyzer, but others have been turned into actual products by other people and companies. I thought of making a multimeter with a wireless detachable LCD years before Fluke actually made that a product.
The latest one someone else has pulled straight from my mind was an idea to make a flexible sensor that can detect how it is bent using flex PCBs and capacitive sensing. My idea was to put it into a glove for detecting finger positions. Just take a couple flex PCBs with capacitive sensor pads and probably a blank layer between and when you bend it one flex PCB will slide on the top of the other and slightly misalign the pads because of the slightly longer path around the outside. I figured you could detect this with capacitive sensing methods. I never made a prototype for a couple reasons. The main one being I get lots of ideas and never get around to acting on many of them. But also, I don't know if my analog design skills are up to the task of designing circuitry that can detect fractions of a picofarad of capacitance change as a couple plates slide maybe a millimeter one way or the other. But someone else has designed this exact thing and it seems to work very well.
https://hackaday.com/2020/06/26/slipping-sheets-map-multiple-bends-in-this-ingenious-flex-sensor/I've actually thought about just posting all my ideas somewhere even if I never actually work on the projects. Like just post them on Hackaday.io as a project concept and just say that it's only an idea that I'm not currently working on. Some people might think "why just give up all your good ideas?" But if someone else does it I get the satisfaction of people knowing I posted the idea first even if I never actually acted on it. And I might get other people to do the actual hard work of engineering my ideas.
And it's very unlikely I'd ever make any profit off "hording" my ideas anyway.