Flowable documentation has a info about creating custom flowable work application for springboot, see https://documentation.flowable.com/dev-guide/3.5.0/525-create-custom-project.html. Is there any way to create custom flowable designer in the same way. If yes, which dependencies I need to import and if no, what are the alternatives?
The Flowable Modeler uses the Oryx Editor.
The documentation you are looking at is for the commercial product. If you are using the commercial product, there is a separate forum to discuss those issues. You can contact your sales rep to get access.
Just for completeness, the open source UI apps do not have starters but the commercial UI apps do.
One more note: there are technically 3 modelers: Modeler (open source and web based), Design (closed source and web based), and Designer (open source eclipse plugin). This section of the forum is for the eclipse plugin, which is almost unmaintained.