Pause and resume as often as you like. Every take lands in the same file; each resume point is marked with a dashed line on the waveform. After Stop, pressing Record again adds more to the end.
Drag across the waveform to select. Drag a selection edge to adjust it. Click to place the playhead. Keys: Space play/stop, Delete cut selection, Ctrl+Z undo, Esc clear selection.
Pause and resume as often as you like; it all lands in one video file. Stopping the share from Chrome's sharing bar also stops the recording. For a custom area, pick Entire Screen (or a window) in Chrome's dialog, then drag the area here. A new recording replaces the current one, so download first.
Downloads follow the trim; with no trim set you get the whole recording. Audio exports right away. A trimmed video re-records that part in real time, so a 2-minute clip takes about 2 minutes; keep this tab in front while it runs. Type times such as 1:02.50 or 62.5 and press Enter.