There is a new version of the Linkage program here:
This new version has a locking feature for locking the size and shape of links. This feature is still being developed so I have not even tried to address link rotation with this new feature. But for moving links, it seems to be working pretty well.
This is more like Alpha software. But since users have asked for this feature, I thought that I might make it available as I work on it.
To use the new locking feature, simply select a link to lock and then click on the lock button in the toolbar. To unlock a link, you need to display the link properties box and then unselect the “Locked” checkbox.
Link Properties Box
I also made some changes to where dimension lines show up on various shapes of links. if a link has it’s longest edge at the bottom of the link, the left-most connector of that edge will be the connector that all measurements start from. This makes the dimensions look more like I expect, and will make them much more typical when the links are displayed in an upcoming parts list display feature.