[Skeleton Tool] Compatibility with Closed Kinetic Chain Movements

[utkb]

Is your feature request related to a problem? Please describe.
I am a physiotherapist and I used Synfig for creating physcial exerise demonstrations. I realized a thing during making animations. We define some exercises as closed chain where the distal aspect of the extremity is fixed to an object that is stationary.

One example:

• Push-up.
• Shoulder bridge

In this movement, foot and upper back must be fixed (chain closed) and the parts between foot and upper back should be free.

Describe the solution you'd like

Could Synfig Studio, provide a way to fix foot and shoulder bones?

Describe alternatives you've considered
Or sometimes my model sit at hip. Could we change most parent bone?

Additional comments
I take the ofical course and i can't find a possible solution. If there is any, thank you for your help and thak you for this great sofware.