After the update of the Line Sidebar only Line and Arrow widget work all other widgets are grayed out and didn't work. In the dialog you can edit them.
Caolán McNamara committed a patch related to this issue. It has been pushed to "master": https://git.libreoffice.org/core/commit/ee6b19259647aae001ff0f4150cbb0483e6786ec tdf#130157 Line Sidebar width, color, transparency, etc didn't work It will be available in 6.5.0. The patch should be included in the daily builds available at https://dev-builds.libreoffice.org/daily/ in the next 24-48 hours. More information about daily builds can be found at: https://wiki.documentfoundation.org/Testing_Daily_Builds Affected users are encouraged to test the fix and report feedback.