This extension adds basic copy/paste and set weight capabilities, common in other 3d editors but for some reason not in Blender:
Copy Weights The operator copies skin weights from the first vertex in the selection. (Usually, you select only one, but there can be different cases)
Paste Weights The operator has two options:
Clear existing weights
removes existing vertex groups for target vertices before the pastingNormalize weights
normalizes weights after pasting if the copied ones were not normalizedSelect loops operator selects an edge loop in Weight Paint mode if at least 2 vertices were selected
Set Weights operator allows setting a precise weight value for selected vertices. You select a starting value(0, 0.1, 0.25, 0.5, 0.75, 0.9, 1), but then you can adjust it in an operator panel that appears in the left corner of the viewport
v.0.3.0
This extension does not require special permissions.