You can set up a new board and save your filter there, as well as any other setting you want (such as what document to view, where in the document to open up to, type of pane [outline, list, etc] and how to group it by). Once you set up the new board and configure the pane the way you want it, right click the name of the board on the side (or top) bar. You can rename the board as well as choose to “Save view as default”. Once it is saved, if you make any changes, you can right click again and choose “Restore default view” and it will bring back the filter (and any other setting you chose).
There is a helpful article with some videos on how this works at:
I also have a list of complex searches I have created stored in one of my documents. By clicking “Advanced” in the filter pop-up box (this maybe a paid feature, I’m not sure), the searches turn from symbols to words and you can make more complex filters. I copy and paste the search terms into my document just in case I some how erase them and then resave the board’s default view by mistake. But this may just be my paranoia and OCD coming through!