Auto adding words with appendixes

I would like to ask if is possible to add function with which will be possible to adding word by appendixes or modification

In slovak and czech language we modify ending of base word and with
this modification we determine person (I, you, they), time
(future/past) etc.

Settings “Compound suggestions” isnt good for this case becouse
germans are using two (and more) whole words which are connected
together, but slovak/czech/russian (and maybe another languages) are using

When I enter word “čítam” (in english it means “I read”) and want to
add into dictionary “čítali” (means “they read”) I must write whole
word “čítali” becouse when I will write only “čítam” and then delete
"m" and write “li” it will not add whole word “čítali” automatically
into dictionary only word “li”.
In swiftkey it works that when I have write “čítam” and then modify
it, into dictionary was added new word (in this example “čítali”)

I know that this is hardly to understand but this issue can be fix
with that keyboard will into dictionary add whole modified word
(“čítali”) not only added part (“li”)