Hi @kharina ,
Do you want to collect a single one record once time when you press the "Save" button?
Based on the needs that you mentioned, I think the solution provided in your previous reply could achieve your needs. I have made a test on my side, please check the following screenshot:

Set the OnSelect property of the "Save" button to following:
UpdateContext({IsStart: !IsStart});
If(
IsStart = true,
Collect(Stamp, {TimeStamp: Text(Now(), "[$-en-US]yyyy-mm-dd HH:mm:ss"), Description: Button1.Text}),
Collect(Stamp, {TimeStamp: Text(Now(), "[$-en-US]yyyy-mm-dd HH:mm:ss"), Description: Button1_1.Text})
)
or
Set(IsStart, !IsStart);
If(
IsStart = true,
Collect(Stamp, {TimeStamp: Text(Now(), "[$-en-US]yyyy-mm-dd HH:mm:ss"), Description: Button1.Text}),
Collect(Stamp, {TimeStamp: Text(Now(), "[$-en-US]yyyy-mm-dd HH:mm:ss"), Description: Button1_1.Text})
)
Set the Items property of the Data Table to following:
Stamp
Please check the following GIF screenshot for more details:

Based on the screenshot you listed in your previous thread, I think there is something wrong with your Collect formula. Within the "Start", "End" and "Toggle" button, you collect a collection (called "Stamp") contains "TimeStamp" and "Description" column. But within your "Save" button, you collect a collection called "stamp" collection contains "timestamp" and "Description" column. The "Stamp" and the "stamp" collection are different collections rather than same one.
Note: The variable name is case-sensitive in PowerApps canvas app.
But according to the Data Table screenshot that you mentioned in previous thread, it seems to be connected to "Stamp" collection rather than "stamp" collection. So please change the Items property of the Data Table control from "Stamp" into "stamp", then enable corresponding fields within this Data Table, check if the issue is solved. Or you could modify the formula within your "Save" button to following:
UpdateContext({Save: !Save});
If(
Save = true,
Collect(Stamp, {TimeStamp: Label5_4.Text, Description: Button4.Text}),
Collect(Stamp, {TimeStamp: Label5_4.Text, Description: Button4_1.Text})
)
Best regards,