The process for "Insert->Sheet From File..." could be improved:
In the "Insert Sheet" dialog, the "Name" field should not be restricted to
"New sheet" but also be active for "From file" to enable the user to assign a
name for the imported sheet.
*** Bug 67481 has been marked as a duplicate of this bug. ***
I can confirm this behavior with LO 126.96.36.199 (Win7 32bit). Should be a valid enhancement request that could make such function better.