SUMMARY with strg + i you can filter an huge folder very quick. It would be nice that you can use the dolphin commands (shortcuts) for the filtered files. This will be possible if the filtered files are also selected by default cause on selected files you can use shortcuts, ... The main benefit whould be that you don't have to switch between keyboard and mouse which is for an file manager very importend cause if you manage file it will be done ordinary by keyboard. STEPS TO REPRODUCE 1. strg + i for jump to filter list 2. search after something 3. use strg + c for copy 4. go somewhere else and click strg + v for past the selected filtered files OBSERVED RESULT in filter list you have to switch to the main view for select stuff where you than can use shortcuts. EXPECTED RESULT if you use the filter bar the items from the main view should be selected by default so you can use shortcuts for the filtered AND selected files.
Copy might be slightly ambiguous since the user could conceivably want to copy the text in the filter bar. But yeah, I understand your goal, which is better integration between the filter bar and the file view. This is sort of a tricky problem to solve, but I agree that it should somehow be done.
Another possible workaround, just enter the filter text, then hit Enter and focus will go to the file view where you can Ctrl+A and Ctrl+C the items. So CTRL+I + Filter Text + Enter + CTRL+A for select filtered items. Maybe the option like "Always select filtered items" in Settings Misc section would be nice to eliminate the CTRL+A step.