It would be convenient if the button would not disappear, but would always be in the side bar of the tools that have dynamic topology.
Or a NEW enable Dynamic Topology Button in the Side Bar.
Unfortunately, when you change the mesh, the button disappears.
It stays on with mesh’s that have DT enabled, I use DT constantly and I’ve never encountered this personally bud, it’s only not there if I haven’t primed the mesh for it.
Yes, but with any other mesh the button disappears.
If you have many single meshes ( 40 different mushrooms 
) this is not practical.
Simple merge and dynotopo ON and separate does not help either.
If you decimate the mesh or do a voxel remesh, the button also disappears.
So you have to open the menu every time and activate the thing there. Click 3 times to reach the goal.
The button could always be there - just grayed out.
The space is there. 
I have many sculpts with different mesh’s enabled with dt, I can swap between these mesh’s and DT (if it was enabled) is there, just tested it with recent piece and there’s easily 30-40 different segments - voxel remesh and decimation alters the topology, therefor the detail scale, and so DT needs to be re-applied, that’s normal behaviour. The button is to enable it for tools, not to enable DT itself. It’s to switch it off for tool use - if it’s greyed out, it means the tool is unable to use it - if it’s not there, the mesh needs to be DT enabled.
I have changed my proposal.
It would be nice to have an ENABLE dynamic Topology button in the side bar.
That saves 2 x button presses.
