Hi @Triplee23 :
Do you want to add records to a subtable in the collection?
My method is to use Split and concat to construct the table to update the data.
The key is to construct a new table as the value to be updated.
Case1:The value of Iterm2 is a single column table
Ceate collection:
ClearCollect(col_test1,{Item1: "Text", Item2: Table({Child1: "Random"})})
Add Record:
Patch(
col_test1,
LookUp(col_test1,Item1="Text"),
{
Item2: RenameColumns(
Split(
Concatenate(
Concat(
LookUp(
col_test1,
Item1 = "Text"
).Item2,
Child1,
"#"
),
"#","Random_new"
),
"#"
),
"Result",
"Child1"
)
}
)

Case2:The value of Iterm2 is a multiple columns table
Ceate collection:
ClearCollect(col_test1, {Item1: "Text", Item2: Table({Child1: "Random"})})
Add Record:
Patch(
col_test1,
LookUp(
col_test1,
Item1 = "Text"
),
{
Item2: ShowColumns(
AddColumns(
Split(
Concatenate(
Concat(
Concatenate(
LookUp(
col_test1,
Item1 = "Text"
).Item2.Child1,
"%%",
LookUp(
col_test1,
Item1 = "Text"
).Item2.Child2,
"%%",
LookUp(
col_test1,
Item1 = "Text"
).Item2.Child3
),
Result,
"#"
),
"#",
"Random_new",
"%%",
"Random_new",
"%%",
"Random_new"
),
"#"
),
"Child1",
First(
Split(
Result,
"%%"
)
).Result,
"Child2",
Last(
FirstN(
Split(
Result,
"%%"
),
2
)
).Result,
"Child3",
Last(
FirstN(
Split(
Result,
"%%"
),
3
)
).Result
),
"Child1",
"Child2",
"Child3"
)
}
)

Best Regards,
Bof