The ENTIRE series (In so far as the universe everyone knows, commonly called the "Trails" universe) is:

Trails in the Sky (FC, SC, Third) (PC, PSP (1-2 officially, 3rd with a fan-patch), Vita (All with Fan-patch))

From Zero/to Azure (PSP (Fan Patch), Vita (Fan-Patch), PC, Switch, PS4)

Cold Steel (1-4) (Vita (1-2 only), PS4, Switch (3-4 only in the west; Fan Patches exist for 1-2), PC)

Reverie (Switch, PS4, PC)

Through Daybreak (Not released yet) (Switch, PS4/5, PC)

- Copy from Reddit @FurbyTime