• The Find what and Replace with fields are the standard search and replace fields.
• Filters allows you to search/replace on *.txt files for example. It defaults to blank which is ..
• Directory is just the directory path of where your files are. Don’t try some path\*.txt as it won’t work…
• Related to Directory is the In all sub-folders checkbox on the right side. That’s enabled by default. You may want to turn it off.

You then will do [Replace in Files] but you absolutely should make a full backup of your files first as [Replace in Files] will promptly do the search/replace on all of the files you are filtering for and save those files. There are no backups made by this process which is why you should make your own backups.

Something that is safer than the [Replace in Files] button is the [Find All] button that is above it. This will scan your files for the Find what pattern and will create a search-results list. You would still need to then click to open the files one by one to test the search/replace.

It seems as if you want to use Mark ing, specifically Bookark ing of lines in order to do your deletion operation, but you want to use it on a multi-file or multi-tab basis. If that’s the case, then, sorry, it doesn’t work multi-tab.

You’ll have to adjust your regular expression to match specifically the data you wish to delete, and then use Replace All in All Open Documents or Replace in Files to replace your matches with nothing, as Scott said.