I've 7 tables. Each table signifies transmission type where each row in table signifies the Trasmission.

Fundamental essentials tables: Tables

A few of the tables have task_reference_id area and a number of them does not have.
What this means is that certain task can recommended by many people tables.
No I must change this structure: Each transmission table with task_reference_id area should mention of the many tasks references.
Which means that I have to add 5 tables with fields: task_id, transmission_id which will contain the tasks references.
But this will make me think, rather than adding 5 new tables maybe I'm able to create parent "Transmission" table that other tables will "inherit" from (primary key is going to be foreing type in parents table).
And the like it will require just one table to create references to tasks. This table may have base_transmission_id, task_id area.

What is your opinion? What will improve: add 5 tables or alter the structure with parent table and so i will need to add only one table to be able to reference the duties?

I'd choose supertype/subtype, here are few examples.