It's normal that TR created for replenishment has no source information. Source storage type/bin should be determined when you convert the TR to TO.
...., will I have to create a new movement type type each time I decide to configure fixed bin replenishment between two set of storage type/bins....
It's not necessary unless you have the following scenario:-
Material A can be kept in fixed bin in s.type XXX and s.type YYY. For XXX, it's replenished from s.type AAA while YYY is replenished from BBB.