ALTER TABLE Syntax

to change table column datatype, add new column, remove column you can use below syntax rather than to modify from design view of table.

--add new column
ALTER TABLE "Tablename"
ADD  "ColumnName" "datatyepe" "constraints"
 
 --alter table column
ALTER TABLE "TableName"
ALTER COLUMN "ColumnName" "datatype" "constraints"
 
 --drop/remove column from table
ALTER TABLE "TableName"
DROP COLUMN "ColumnName"

datatype can be any valid datatype of sql and constraints is any like not null, null, primary key etc..