TMS Diagram Studio is VCL only but there is now TMS FNC Blox which is a cross-platform solution for diagramming: https://www.tmssoftware.com/site/tmsfncblox.asp
Two questions on the subject of VCL DIagram and FNC Blox:
TMS FNC Blox can be used with TMS WEB Core.
Diagram Studio is a 100% VCL product and cannot be used in TMS WEB Core.
There are a lot of similarities between TMS FNC Blox and TMS Diagram Studio but products do not have feature parity nor file compatibility. TMS FNC Blox was created & designed from the ground up for cross-platform, including web support and therefore several changes were needed to achieve this.