Hi Dennis

Thanks for posting in the community! Immediately after dragging a "shape" (equation) from the Equations library onto your document an editor pop-up will appear which gives you the ability to type a custom equation in LaTex. If you're attempting to place an equation into a flowchart shape you can group the two shapes together by holding down Command or CTRL and left clicking on the shapes you want to group. After selecting the shapes you want to group click the "Arrange" dropdown on the top toolbar and click "Group". Please let me know if you have further questions. 

Would it be possible to eventually implement this inside normal shapes - i.e. by placing LaTeX entries between $$?

Hi there

Thanks for posting in the community. LaTeX entries aren't currently supported for flowchart shapes, but we’re very interested in your feedback and committed to continually improving our products. Please first search the Product Feedback section of this community (with the filter Topic Type = Idea) to see if it’s already been submitted. If so, please add any additional details you’d like and upvote the request - this consolidation helps to refine feedback and properly capture the popularity of the request.

If no one has submitted this idea yet, please create one of your own and be sure to include details about your use case or what you’d like to see in this experience. This will also allow other users with similar requests to discover and upvote it, then add details of their own.

Finally, for more information on how Lucid manages feedback via this community, take a look at this post: