Syntax:
matrix://MBookName: Insert a link to a matrix book, given by MBookName, so the matrix book will be displayed in the current worksheet cell.
matrix://[MBookName]MSheetName: Insert a link to a matrix sheet, given by MSheetName, so the matrix sheet will be displayed in the current worksheet cell.
(Note: Insert a link to a matrix object syntax is matrix://[MBookName]MSheetName!MatrixObjectName, which is already supported before Origin 2019.)