# Basic syntax:
=FILTER({A3:A12; B5:B7}, LEN({A3:A12; B5:B7}))
# Where:
# - this stacks the non-empty cells from the ranges defined in columns
# A and B
# - {range_A; range_B} stacks the defined ranges
# - FILTER with LEN is used to exclude any empty cells. This works
# because LEN returns a number other than 0 for each cell that
# contains content. This non-zero number is then treated as "True"
# by FILTER, causing only those cells to be kept
# Note:
# - if you don't mind including blank cells (or you don't have any),
# you can just use {} without FILTER to stack columns