Can it be done with our without an extension?
Basically this is a configurable product that shows a different set of options depending on a selection already made. Quantity pricing might change as well depending on selection. Total price is updated on product page. No need to put into cart. See this example please. Don't need a custom design feature, just logo upload.

https://www.discountmugs.com/product/db13-persoanlized-duffel-bags/

So this would be: Product's Sort Order Low > High

Cool, works.

Now how can I efficiently put sorting numbers in each product for a certain category? All I see is set a filter for the cat then edit one product, save then go back and set filter again (filter got lost after going back) edit the next product..... very inefficient. Is there a better way available?

Absolutely still needed. Has there been any progress on this? I need control over how my products are sorted on initial load of the category where they are displayed. Now I have to edit each product to give it a sort value. Very time consuming.

I think this is not what I am looking for. I want to bulk apply a discounted price to a group of products. Not a promotion that will be applied in the cart. I want the discount to be shown on each product. Like was $25 now $19.99. See picture for an example of a sale.

How can I put several products on sale? Say I want to put everything on sale or just certain products that I select. Any way of creating sales other than editing every single product?

What is the status on an admin solution for this as it was posted some time ago? Can I manually copy some folders or is it not possible? Please point me the right direction for modifying the default template so my changes get retained when Abantecart is updated. It think for now I only need to make CSS changes. Are there any override directories where I can upload the changed CSS?

I did see the first post here for the option to use Developer Tools. Seems complicated just to make a copy of the default template. Is there another way? Or should I dig in and install Developer Tools?

Or just make the CSS changes on the original template and keep a copy for use after next upgrade?

I want to clarify my suggestions a bit better. I'm not set on having a One Page Checkout but would like to see an optimized checkout with less steps.

Shopping Cart – Checkout Optimization
My suggestions to improve customer experience and avoid abandoned orders.
1.   Progress indicators. The customer should know where they are in the process and what else needs to be done to complete the purchase.  One way to achieve this is to have a progress bar across the top of each checkout page.
2.   Shorten the checkout process by combining account creation (shipping / billing info) with selecting shipping options and payment options.
3.   Optional if possible: Maybe move the decision to create an account to the end of the process by simply asking them to provide a password to allow an account creation. Otherwise if not provided simply treat this as a guest checkout.

Shopping Cart Page
Calculation of shipping is possible but displays a drop down box. Customer has to click on the drop down arrow to see all available shipping options. I would rather have a table showing all shipping options right away. Maybe radio button selection instead of the drop down. A functionality in the dashboard to switch on to display the cheapest shipping method first or as default selected would be helpful. (Not sure if this is possible already). Retain the selection of shipping option for the next page.

Pressing Checkout leads us to the Account Login page. Assuming here we simply continue with Guest Checkout.
Guest Checkout - Step 1: Combine this step 1 page with step2 and possibly 3.

Currently the step 3 is titled CHECKOUT CONFIRMATION. Well, this is somewhat misleading. This is not yet the checkout confirmation. It is the order summary with whatever info was collected so far but we still ask for the payment info on this page and an action to confirm the order. Only then do we get to the actual order confirmation page. On the order confirmation page we should display the order number too btw. Maybe this is already an option?