Hello soulartist, those lines are Layout Guids.
When not in use their “icons” can be found in the top left corner of the UI / Canvas and can be dragged out over the canvas as guid lines.
The guides can be shown/hidden and further edited via the Layout panel accessed from AR’s menubar by clicking on the # icon found there.
You can read more about their use here: https://www.artrage.com/manuals/graphic-design/guides/
Maker Of Replica Macoys
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Thank you Markw for the information