In the family table for this part, right click on the BASE column header and choose Column Properties.  In that dialog, you can specify that this be a custom column and specify the range of values that it can have.

Hi Jan, thanks for the reply!So, i follow your screenshot steps and it worked for some of the channels, however it doesn't work for all of them somehow, do you have any clues why?PS: Last image i made exemples of it, i placed all of those with "COMPRIMENTO" (Length) of 1000mm and note that not all of them gets the same length.

I made it appear that i can select now the value i want, however, when i place it, it stays at 10mm, even though i wrote another value for "comprimento" (Length), see in the images below.

Is the column values for that column in black or blue (values)?   Is that column mapped to the length value in your part?  Can you share the part making this?   (Also specify Inventor version too)..

Hello everyone,So, i published a type of channel that is not in inventors standards and im having difficulties with the length when i place it as a part in an random assembly, (see image below), my problem is that when i try to place it, i want it to have a variable length like the user typing the length of the extrusion he wants for that specified channel, so, for exemple, if i place it, it will always have "comprimento" (Length) of 10mm.

all seems to be OK with your profile/frame. You just need to make sure, your Content Center table column COMPRIMENTO  is mapped to the template parameter riding length. For steel shapes / frame such column is mostly B_L. Such iPart column (and Content Center table column) needs to be Custom/Range to allow enter distance when placing.

Column for "comprimento" is now blue (see image 5);When i designed that iPart for publishing, i made the extrusion of the channel linked to "COMPRIMENTO = 10mm"  (see the file below).

Yes..  Select Expression and then custom formula.   From there, enter the min and max length, the default and the incremental values.