Textboxes can be added to shapes via context menu -> Add Text Box since 4.4.0.3.
For reference, this commit added the context menu entry: https://cgit.freedesktop.org/libreoffice/core/commit/?id=7f77b8a689f84a03495ac5911236b68f01ee7b24 author Miklos Vajna <vmiklos@collabora.co.uk> 2014-06-19 10:11:10 +0200 committer Miklos Vajna <vmiklos@collabora.co.uk> 2014-06-19 11:29:31 +0200 sw: add UI for adding a textbox for a draw shape