I recently did a road bike event while a few steep climbs. I felt myself sliding back in the saddle to the point where when the road eventually leveled off I had to stand up and reposition myself forward Kind of felt like I was going to slide off.
Would you consider this normal as the body is trying to apply more leverage or does the saddle need to be raised or does the saddle need a more forward position?
If a climb is steep enough, I would aggressively lean forward and tension my arms. Not quite getting out of the saddle, but just-about.
This shifts more weight to the front wheel, which for me gets a little "lifty" on the steep climbs. The steepest gradient is therefore limited to an angle where I can keep the front wheel on the road while maintaining some forward speed above 4 km/h. Any less and I am doing more of a long-trackstand and spend too much effort on balancing instead of going forward, eventually having to put a foot down and then it's always too steep to start.
As for sliding around on the saddle, this could be tweaked in two ways.
Adjust your saddle's angle so the nose is down a little. If your saddle is a single-bolt design you might have to move it a whole tooth, or if its a two-bolt design then just a couple of turns looser on the rear then the same tighter on the front bolt.
Is your saddle too narrow? As we age, our ability to conform to the bike decreases. It may be that a saddle with a wider sit-bone area may reduce your rearward slide tendancy.
Saddle position is a compromise between climbing and flat-land (downhill is less-important) so mind that any adjustments to help one don't hinder the other.
IT IS normal when climbing seated to slide back a bit in the saddle for more leverage, as you pointed out. It is subtle and should not feel like you are falling off the back of the saddle. If that is the case, then you might look at raising the saddle slightly and/or get a bike fitting (highly recommended).
Saddle height is usually set to be as ideal as possible for a flat riding condition for a rider. Everyone has a slightly different geometry and flexibility, which is why I added the "as possible" to the setting. When climbing while seated, one will naturally slide a bit back in the saddle for additional leverage. It usually is almost done unconsciously. Another example of moving in the saddle is when riding hard on the flats, low in the drops of the handlebars. The rider will slide forward, again unconsciously, until they are on the nose of the saddle (which is not necessarily comfortable over a long period!). This is purely to provide additional power when staying low up front by altering your geometry. This position is sometimes called "on the rivet" because older saddles (Brooks) had a metal rivet on the nose of the saddle. So if you are riding "on the rivet" you are drilling it hard, while staying low up front for aerodynamics.
Another thing I would consider is a saddle that has a curved / waved shape. With the saddle rear bending upwards.
The worst type of saddle for the problem you are describing would be one that is flat, very hard (like those carbon ones, your seatbones won't "dig" into it), and with a slippery surface. If you have one of those, the main adjustment you can do to improve your problem is to angle its nose down, but then you will be sliding forward on flat roads, and your hands may go numb from the extra weight shifted on them.
The curved saddle offers good stability in both worlds.
It is very easy to adjust the tilting of the bicycle seat, usually you only need to release a nut under the seat, move the seat into another position and tighten the nut again. It is beneficial to learn doing it yourself because you may need some riding before understanding if the new setting is actually better.
You probably do not need to re-adjust the tilting every time switching from uphill to downhill but is it seldom adjusted in the factory exactly how do you personally prefer.
