Change the number of toolbars in a document also changes the toolbars i the corresponding template. How can I avoid this? Lo

The change is independent of the location of the template. It even happens in root owned templates ie in /opt/libreoffice6.1/share/template/common/styles.

Mike, hope this clarifies things:
This is the original standard template set as the default template.

This file is created w. the standard template.

Two toolbars are added to the created file. View > Toolbars > Formatting; View > Toolbars > Formatting(Styles)
Below is the document with the toolbars added.

This is well and good. BUT the standard template should not change . But to my surprise this happens.
Standard template after the untitled document has been closed.

Are you really saving the toolbar preferences to the file? Please describe your procedure, so that it’s obvious to others what is obvious to you…

The toolbar state controlled by View menu is not related to documents, and is saved to user settings. So it applies to any document, no matter what template was used for its creation. That is normal behavior.

If you need a setting specific to a document, you need to use ToolsCustomize... dialog, and on Toolbars tab, select your currently open document as Scope - so that those settings would be saved with the document.