insert a bookmark

Click in a line, and then press Ctrl+Shift+B.

insert a bookmark on every line that contains a text string

Open the Find pane, enter a search string, and then click Mark All.

A bookmark is inserted on every line that contains the string. If a line already contains a bookmark, the bookmark is deleted.

move to the next bookmark in the current file

Press Ctrl+Shift+N.

move to the previous bookmark in the current file

Press Ctrl+Shift+P.

delete a bookmark

Click in the line that has the bookmark, and then press Ctrl+Shift+B.

delete all bookmarks from the current file

Press Ctrl+Shift+A.