There is no option to remove all tags from all source segments at once in the editors.
Available workaround (if any):
Via F2 button, the source segment can be edited and the tag(s) removed. However, it needs to be done one by one.
Add an option to remove all tags from all source segments at once. Like it works for target segments with Ctrl+F8 shortcut.
It would enable to clear the content for TM. Especially in case, the tags are not necessary (format tags).