1. open writer
2. activate print preview
3. notice 'close preview' button has text
4. customize the print preview toolbar and hide the button by unchecking it
5. without closing the dialog, check it again and now an image appears rather than the button text
So unchecking the entry simply adds the toolbar:visible attribute to the entry, but checking it again removes the toolbar:style attribute.
Build ID: 2618e4a13d719122e6358d9d96864d1691e56a02
CPU threads: 2; OS: Linux 4.4; UI render: default; VCL: gtk2;
Locale: en-US (en_US.UTF-8); Calc: group threaded
Confirmed with the daily master for Windows from today, also described in comment 0 of bug 114265.
Maxim Monastirsky committed a patch related to this issue.
It has been pushed to "master":
tdf#114261 Retain toolbar:style after customization
It will be available in 6.1.0.
The patch should be included in the daily builds available at
http://dev-builds.libreoffice.org/daily/ in the next 24-48 hours. More
information about daily builds can be found at:
Affected users are encouraged to test the fix and report feedback.