something else I found out. but it's no logic thing. when I make duplicate version from orig mesh and map it planar, then try to transfer the new UVset_Costum to the orig mesh it happens that this creates nothing. so I try it again - same process. well the 2nd try did work it created beside the default map1 a UVset_Costum on my original mesh. there is absolutely no logic sense about this. why didn't it work the first time?! there was no warning in the SE. after deleting the new set transfering still doesn't work the first but second time.

first try:

select -r polyToSubd55 ;
select -tgl polyToSubd54 ;
polyTransfer -vc 0 -uv 1 -v 0 -ao polyToSubd55|subdTessShape2 polyToSubd54|subdTessShape2;
// Result: polyTransfer1 //


second try:

select -r polyToSubd55 ;
select -tgl polyToSubd54 ;
polyTransfer -vc 0 -uv 1 -v 0 -ao polyToSubd55|subdTessShape2 polyToSubd54|subdTessShape2;
// Result: polyTransfer2 //


after deleting the UVsets I also deleted history. next try is with a extracted part. extracted the dupe mesh in two halfes maped it planar. no transfer is happening.

SE:
select -r polyToSubd55 ;
select -tgl polyToSubd54 ;
polyTransfer -vc 0 -uv 1 -v 0 -ao polyToSubd55|subdTessShape2 polyToSubd54|subdTessShape2;
// Warning: Can't perform polyTransfer1 on disabled selection //
// Result: polyTransfer1 //



I would be so very happy if someone could tell me something about that!