With the various properties found in the Image content panel are being added to the image tab of the image dialog (bug 103272), the Image content panel title should get a 'More Options' button to link to the image dialog.
Very easy hack. Sidebar config is in officecfg/*/UI/Sidebar.xcu. Look for GraphicPropertyPanel and tweak its ContextList so it contains the corresponding UNO command to open the dialog on clicking 'More options' button. But only for Writer. Afaics the dialog is not available for ImpressDraw and Calc
Arnold Dumas committed a patch related to this issue. It has been pushed to "master": http://cgit.freedesktop.org/libreoffice/core/commit/?id=7d21ae342dc5c4d4c3a4f3f5c2603b7b6be84d00 tdf#104507: Add a 'More Options' button to Image content panel It will be available in 5.4.0. 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: http://wiki.documentfoundation.org/Testing_Daily_Builds Affected users are encouraged to test the fix and report feedback.