You may wish to have multiple Master tables for a given Project. For example, you may want to reserve one Master table for historic data which are bulky but rarely used, one for meteorologic data, and one for field data taken during intensive field surveys.
Create a new Master table by selecting File | Project Preferences. Then select the Create button to create an empty Master table, ready to accept transferred data from a Working table (see Transfer Data from a Working Table to a Master Table).