in the TL the in/outs are the little yellow triangles above the timeline time. They have the lines going down. When you use the mouse to drag+select it says an in/out time + selection duration all the way to the right of the record/loop/play @ start/play/etc. buttons. When you use the i/o it just displays the duration time. You can left click on the selection vertical line & the playback head will snap to it (if enabled). You will know if you snapped because it will highlight blue when you click on it. Hover the courser over the little triangles/selection area to get the in/out times. Double click on any selection area to select it & get the in/out times in the display on the play bar right side.

Trimmer works the same but not vertical lines (no reason, you're only dealing with a single AV track vs unlimited tracks).

You can't clean the in/out locations. No reason to. They don't do anything if you don't have anything to paste/copy related to them. You don't loop playback unless looping is enabled & you're inside the loop. If you mean to delete the stuff in the in/out area (parts of media) you just hit the DEL key. To have it only effect one event if there's multiple on the track in the selected area you left click that event then double-click the blue selection area, then hit delete. If you want to paste something in another area you'd click on the track/location & then paste/insert media. Any place you click after the range (in/out) is made overrides the paste location.

You can't delete stuff in the trimmer, it wouldn't make sense. In/out isn't saved with the file so there's no reason to delete it. The in/out is saved with the file as long as you have the project open so you can always go back & see what your previous in/outs were. Ranges work in the trimmer too & can be saved with the file to keep multiple in/outs on record.