How we can see on image sleeve draw was rotated and above of two pattern pieces was drawn new pattern piece that use parts of both.
This may be related to #335 "Add Multidocument Mode feature"
This may be related to issue #258: Add 'Tracing Mode', in that it requires the definition of a base layer plus a design layer which overlays the base layer.
This may require issue #338: Add Rotate Pattern tool (Trueing shoulder) to manipulate the placement of pattern pieces in the base layer.
The user would open an existing pattern and assign it to the 'base' layer.
The user would rotate the pattern pieces in the 'base' layer.
The user cannot change the formulas in the 'base' layer (they can do this separately if needed, then open the changed pattern).
The user would design new points, lines and curves in the top 'design' layer.
The user can use the points, lines, and curves from the 'base' layer pattern in the formulas. (This may require a prefix to the 'base' layer objects to distinguish them from the new design points.)
The user saves the pattern which includes the 'base' layer pattern's formulas and arrangement.
Opening the saved pattern would show the arranged old pattern in the base layer and the new pattern in the design layer.
Import multiple block patterns to base layer 0.
Join the block patterns together and establish connections between them in layer 1.
Make design changes in layer 2.
The Pattern file is saved from layer 2.