What is the best way to merge multiple tabs with differently sourced data into a main table now that write to table is deprecated?

Use Send table data to transfer rows from multiple tabs into your main table. Go to each source tab, click Actions → Send table data, select your main table as the destination, choose Send row, map the columns you want to transfer, and click Save. When you first send a row, it creates a new row in the destination table; subsequent sends update that same row. Note that data can only flow in one linear direction (A → B → C), and you can connect a maximum of 10 tables. [clay.com