Currently selecting a section of a layer and transforming it is possible in the desktop version but not the mobile version.
It is an incredibly useful feature for adjusting proportions during rough sketching.
Currently it can be done only through a tedious workaround that I'm sure could be automated, at the cost of lowering the maximum layers per file by 1.
This can currently be done by duplicating a layer and the making a selection with the selection tool. Then clear or erase everything inside the selection on one layer and outside the selection on another. Transform the layer containing the selected section as needed and then re-merge the layers back into one.
I'm sure a way to automate this process (at the cost of the availability of one layer from the potential maximum, being reserved for temporary duplication) can be found.
