i have 2 question

hi
Is there a way to delete lines after creating them? I would think there is one but I cannot seem to find it.

and

Is there a way to make circles or essentially non-linear lines with the tool?

thx all

You can use Data module or Annotations module to delete rulers.

For drawing circles, you need to use some Python scripting - see this example: https://www.slicer.org/wiki/Documentation/Nightly/ScriptRepository#Manipulating_objects_in_the_slice_viewer