How would you Document a StagingArea

Question

Hey Folks, i have to document a staging area. But i have problems by document the realtion between the diffrent databases.

i want to do something like that

Table 1(DB 1)                  Table 2(DB 2)
Column 1         ETL logic->   Coulmn 1

I tried out Visio but i didn't found the right shapes which would fit my needs.

Are there expirienced people wich now some tools which fit this requierments?