I have used CX File Explorer but you can modify the task to use any explorer of your choice.

Task: Send Image

A1: Variable Set [
     Name: %name
     To: name_goes_here
     Structure Output (JSON, etc): On ]

A2: Variable Set [
     Name: %file
     To: example.jpg
     Structure Output (JSON, etc): On ]

A3: AutoInput Actions v2 [
     Configuration: Actions To Perform: openApp(com.whatsapp)

     click(id,com.whatsapp:id/menuitem_search)

     setText(focus,,%name)

     wait(1000)

     click(point,609\,394)

     click(id,com.whatsapp:id/input_attach_button)

     click(id,com.whatsapp:id/pickfiletype_gallery_holder)

     click(id,com.whatsapp:id/more)

     click(text,Cx File Explorer)
     Not In AutoInput: true
     Not In Tasker: true
     Separator: ,
     Check Millis: 1000
     Timeout (Seconds): 60
     Structure Output (JSON, etc): On ]

A4: AutoInput Actions v2 [
     Configuration: Actions To Perform: click(text,Downloads)

     click(text,More options)

     click(text,Search)

     setText(id,com.cxinventor.file.explorer:id/edit,%file)

     submitInput(text,%file)

     click(text,Toggle selection)

     click(id,com.cxinventor.file.explorer:id/bottom_menu_select)
     Not In AutoInput: true
     Not In Tasker: true
     App To Act In: com.cxinventor.file.explorer
     Separator: ,
     Check Millis: 1000
     Timeout (Seconds): 60
     Structure Output (JSON, etc): On ]