I would like to create a bill to pay my worker, and retain a % as his saving, payable to him much later after accumulating. How do I create this?

I'm here to guide you through creating a bill to pay your worker and retaining a percentage as his saving in QuickBooks Online (QBO), @acoduman. 

First, let's set up a liability account to track your worker's saving. It's because this is a deduction from the bill you'll create for them. Please take note that you'll need to convert the percentage into an amount as his saving. Before that, I'd recommend consulting your accountant to determine the appropriate account and detail types for this. Once confirmed, proceed with the steps below. 

1. Go to Accounting from the left menu.
2. Select Chart of Accounts.
3. Click New.
4. Select the appropriate Account Type. 
5. Choose the correct Detail Type. 
6. Enter the account name, such as Saving For My Worker. 
7. Click Save and Close.

See the screenshot below to show you the last four steps. For the detailed instructions, check out this article: Adding Accounts. 

Second, let's create a bill and add the liability account you've created above on the second line. Then, enter the amount in negative to increase this account's balance. This way, you'll be able to pay your worker's saving after it accumulates later. Here's how:

1. Go to + New button from the left menu. 
2. Select Bill under Suppliers. 
3. Choose your worker from the Supplier drop-down. 
4. Select the Terms. Enter the Bill date, Due date, and Bill no. 
5. Go to the Category details section. 
6. On the first line, select the expense account and enter the corresponding amount. 
7. On the second line, choose the liability account and enter the amount in negative. 
8. Click Save.

The screenshot below shows you the last six steps. For your reference, kindly refer to this article: Entering Bills. 

Once done, you can go to the Pay Bills option from the + New menu. Just select the bill you've entered above so you'll be able to pay your worker. 

As for the saving, let's create an expense once it accumulates soon. Then, choose the liability account in the Category column. Enter the amount in positive to offset its balance. View the screenshot below for your visual reference. 

Also, I recommend running the Account QuickReport of the liability account. Just locate it from the Chart of Accounts page. Then, click Run report from the Action column. From there, you'll be able to keep track of all the transactions associated with this account, such as your worker's saving. I've attached a screenshot below on how the report looks like in QBO.

Please know that I'll be right here to help if you need anything else. Take care always, @acoduman.