If you have executed a search query but the list of matching issues doesn't fit in a single page, don't worry, you can select all of them in just one click.
What exactly do you have to do? Say you've searched for all your unresolved issues:
for me #unresolved
Found 1000 issues. Now, press Ctrl+A, or click "Select All" on the toolbar to select all issues on the current page. You will notice a message right above your issues: "Click to select all 1000 issues".
Click the link specifying the number of issues to select. Now, you can modify all found issues with the Command window - for example, ty